Veniaminof

United States

56.17°N, 159.38°W; summit elev. 2507 m

All times are local (unless otherwise noted)

AVO reported that seismic tremor was detected at Veniaminof on 12 June. Elevated surface temperatures were detected in satellite images at 0525 on 13 June, likely indicating an intra-caldera eruption. In response, AVO raised the Volcano Alert Level to Watch and the Aviation Color code to Orange. Seismic tremor continued that day, indicative of low-level effusive activity and small explosions. At 2323 a pilot observed ash at an altitude of 3.7 km (12,000 ft) a.s.l. and a lava flow effusing from the intra-caldera cinder cone. Residents in Perryville (32 km SSE) and Port Moller (77 km WSW) also observed ash emissions at about 2330. During 15-18 June satellite images showed very high elevated surface temperatures at the intra-caldera cinder cone consistent with continued lava effusion. No plumes were observed in satellite images nor reported by pilots or local observers. Volcanic tremor continued to be detected.

Geologic Background. Massive Veniaminof volcano, one of the highest and largest volcanoes on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3700 years ago. The caldera rim is up to 520 m high on the north, is deeply notched on the west by Cone Glacier, and is covered by an ice sheet on the south. Post-caldera vents are located along a NW-SE zone bisecting the caldera that extends 55 km from near the Bering Sea coast, across the caldera, and down the Pacific flank. Historical eruptions probably all originated from the westernmost and most prominent of two intra-caldera cones, which rises about 300 m above the surrounding icefield. The other cone is larger, and has a summit crater or caldera that may reach 2.5 km in diameter, but is more subdued and barely rises above the glacier surface.